1. Field of the Invention
The present invention relates to a recording data processor for processing recording data for image recording.
2. Related Background Art
In a conventional processor of this type, input multicolor print information is analyzed and converted to print dot data of the respective colors which is supplied to a multicolor printer such as a two-color laser beam printer shown in FIG. 4.
FIG. 4 shows a sectional view of a two-color laser beam printer capable of multicolor printing. Numeral 21 denotes a photo-sensitive drum which is rotated in the direction of arrow A at a constant speed, numeral 22 denotes a primary charger for uniformly charging a surface potential of the photo-sensitive drum 21, numeral 23 denotes a primary exposure beam which is on/off modulated by red print dot data of input multicolor print information and scans the photo-sensitive drum 21 to form an electrostatic latent image corresponding to red dots and, numeral 24 denotes a red developer which develops the electrostatic latent image formed on the photo-sensitive drum 21 by red toner. Numeral 25 denotes a secondary charger which uniformly charges the surface potential of the photo-sensitive drum 21 to a secondary charge level after the primary development process, numeral 26 denotes a secondary exposure beam which is on/off modulated by black print dot data in the input multicolor print information and scans the photo-sensitive drum 21 to form an electrostatic latent image corresponding to black dots, and numeral 27 denotes a black developer which develops the black electrostatic latent image formed on the photo-sensitive drum 21 by black toner, numeral 28 denotes a transfer charger which transfers the developed black toner and red toner to a record sheet 30, and numeral 29 denotes a separation charger which separates the record sheet 30 fed from the transfer process from the photo-sensitive drum 21. Numeral 31 denotes a cleaner which collects toners of the respective colors remaining on the photo-sensitive drum 21 after the image formation process and cleans the surface of the photo-sensitive drum 21, and numeral 32 denotes a fixing unit which applies heat and pressure to the toners of the respective colors on the record sheet 30 at the end of the transfer process to fix the toners of the respective colors onto the record sheet 30.
The multicolor print process is similar to a known electrophotographic process and hence detail thereof is omitted. It is processed in the order of primary charge, primary exposure, primary development, secondary charge, secondary exposure, secondary development, transfer, separation and fixing.
FIG. 5 shows a block diagram of a prior art multicolor print data control unit. Numeral 41 denotes a CPU which collectively processes the input multicolor print information. Numeral 42 denotes a page buffer which stores one page of the input multicolor print information (print control code, print character code, etc.)45. Numeral 43 denotes a font memory which stores a font pattern for each print character code, which is to be converted to a print dot pattern corresponding to the print character code stored in the page buffer 42. Numeral 44 denotes a bit map memory which stores one page of print dot pattern and sequentially supplies it to a printer (not shown) as serial data 46 in accordance with the print status of the printer under control of a CPU 41.
FIG. 6 shows a configuration of the bit map memory 44 shown in FIG. 5. Numeral 51 denotes a bit map memory for a first color. It stores one page of bit map of, for example, red print data of the multicolor dot pattern data 55. Numeral 52 denotes a bit map memory for a second color. It stores one page of bit map of, for example, black print dot data in the multicolor dot pattern data 55. Numeral 53 denotes a shift register which converts red parallel dot pattern data 56 read from the first color bit map memory 51 to serial red print dot data 58 in accordance with a load signal 60 and a dot clock 61 supplied from the CPU 61 and supplies it to the printer. Numeral 54 denotes a shift register which converts the black parallel dot pattern data 57 read from the second color bit map memory 52 to serial black print dot data 59 in accordance with the load signal 60 and the dot clock 61 supplied from the CPU 41.
When the CPU 41 receives the multicolor print information 45, it stores one page of the analyzed print character code in the page buffer 42. Then, it refers the font patterns corresponding to the print character codes stored in the font memory 43 and converts the input print character code to the multicolor dot pattern data 55 and develops one page thereof into the bit map memory 44. The print dot pattern data corresponding to the first color is developed into one page of the first color bit map memory 51, and the print dot pattern data corresponding to the second color is developed into one page of the second color bit map memory 52. Then, the red parallel dot pattern data 56 developed into the first color bit map memory 51 is transferred to the succeeding stage shift register 53 in synchronism with the load signal 60 and the dot clock 61 supplied from the CPU 41, and the parallel data is converted to the serial red print dot data 58 and is transferred to the printer. With a predetermined time difference, the black parallel dot pattern data 57 developed into the second color bit map memory 52 is transferred to the succeeding stage shift register 54 in synchronism with the load signal 60 and the dot clock 61 supplied from the CPU 41 and the parallel data is converted to the serial black print dot data 59 and it is transferred to the printer. In accordance therewith, the primary exposure beam 23 and the secondary exposure beam 26 shown in FIG. 4 are emitted from a semiconductor laser (not shown) so that the electrostatic latent images of the respective colors are formed on the photoconductor drum 21. In this manner, the multi-color image is developed with the toners of respective colors.
Since the multi-color dot pattern data 55 is independently developed into the bit map memories of the respective colors, that is, the first color bit map memory 51 and the second color bit map memory 52, if the print dots are set at the same address, the red and black dots are mixedly developed at the same position on the photoconductor drum 21 and desired multicolor printing is not attained, but instead a low grade mixed color printing is attained.
In order to resolve the above problems, Japanese Patent Laid-open No. 62-81669 (laid open on Apr. 15, 1987) and Japanese Patent Laid-open No. 62-230160 (laid open on Oct. 8, 1987) were proposed but further improvement has been desired.